METALLOTHIONEINS CONTRIBUTION IN THE RESPONSE OF BIVALVE MOLLUSK TO GLYPHOSATE, PHARMACEUTICALS AND TEMPERATURE CO-EXPOSURE

Specific response of low weight cellular thiols metallothioneins (MTs) to transitional metals is well known. Their targeting by other impacts on the organism is studied less. The aim of this study was to elucidate whether MTs are involving in the response of bivalve mollusk to mixed exposure to the priority pollutants and heating. We treated the mussels Unio tumidus Philipson, 1788 (Unionidae) with drugs diclofenac (Dc, 2 nM), nifedipine (Nf, 2 nM) or organophosphonate herbicide glyphosate (Gl, formulation Roundup MAX, 79 nM) separately at 18o C and in co-exposures at 18o C (DcNfGl) and 25o C(DcNfGl+T) during 14 days. MTs of digestive gland were eluted by size-exclusion chromatography and assessed from the metal composition (MT-Me (Zn,Cu,Cd)) and thiols (MT-SH). All exposures, particularly Gl-contained, increased MT-SH concentration (by 26-48%), detecting the stress response. Dc increased the level of MT-Me, whereas Gl decreased it (by 41%). All Gl-contained exposures increased the part of non-metalated MTs and lactate/pyruvate ratio in the digestive gland. Nf decreased this ratio, up-regulating pyruvate concentration. Shared effect of Nf-contained exposures was the increase of the lysosomal membrane stability in hemocytes. Both co-exposures increased the number of hemocytes with nuclear abnormalities by 1.5-1.7 times indicating the magnification of individual impacts and exceeding of the adaptive limits of the organism in the conditions approximated to the environmental reality. Multivariate statistical analyses confirm the major contribution of MTs into the responses of mollusks, negative correlations in the pairs MT-SH/MT-Me and MT-SH/pyruvate, and distinguish the Gl and DcNfGl+T from other groups.